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By: Michael J. Fevola, PhD, Johnson & Johnson Consumer and Personal Products Worldwide
Posted: April 5, 2011, from the April 2011 issue of Cosmetics & Toiletries.
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The PQ-7 used in personal care applications is typically supplied as a clear, colorless aqueous solution with values of pH = 6.0–7.5 and pH = 3.3–4.5 for paraben-preserved and sodium benzoate-preserved solutions, respectively. Due to the high MW of most PQ-7 type polymers, the solutions exhibit viscosities of ca. 7,000–15,000 cP, yet they contain only 8–10% w/w active polymer solids.3, 5, 12–13
Grades of PQ-7 with lower values of MW and charge density are available and contain up to 40% w/w solids with solution viscosities of 1,200–4,000 cP.3–5 Potential impurities in solutions of PQ-7 may include residuals such as trace (ppm) levels of AM, up to 1.5% w/w DADMAC monomer, polymerization initiators and decomposition products of polymerization initiators, in addition to additives used during the polymerization process—e.g., chelating agents, pH buffers, etc.
PQ-7 type copolymers are broadly deployed in a variety of industrial applications, including water treatment, mineral processing and paper manufacturing.2 In cosmetics and personal care formulations, PQ-7 functions as an antistatic agent, a film-former and a hair fixative,1 although it is more generally recognized as a conditioning agent for hair and skin. PQ-7 has been shown to be highly substantive to keratinous substrates,14, 15 and it is a favorite as an inexpensive yet highly effective conditioning agent in rinse-off formulations such as shampoos, rinse-out hair conditioners, body washes, liquid hand soaps and bar soaps.
PQ-7 can also be used to modify the lathering properties of surfactant-based cleansers and shaving creams since it decreases foam bubble size, increases foam stability and provides slip, leading to richer, creamier, more lubricious foams. Its use in leave-on formulations also has been reported for applications including hair styling and skin moisturization.
PQ-7 is typically employed at 0.1–0.5% w/w active polymer solids in most formulations. In terms of formulation compatibility, PQ-7 is more forgiving than PQ-6 due to its lower charge density and it is readily combined with solutions of anionic surfactants and polymers to provide clear formulations. Solutions of PQ-7 are generally mixed into formulations near the end of the batch process and do not require heating or other special processing conditions. Reproduction of the article without expressed consent is strictly prohibited.